In wavelength multiplexing communication, communication rates are requested to be increased with increases in communication traffic. As a method for increasing the communication rates, there is a method for improving the efficiency of use of frequencies in optical bands. For example, in Orthogonal Frequency Division Multiplexing (OFDM) and Nyquist-Wavelength Division Multiplexing (Nyquist-WDM), multiple channels may be allocated in a narrower frequency band than conventional techniques, and the efficiency of use of frequencies may be improved.
A transmission system is considered, which achieves a communication rate of 100 Gbps or higher by applying a super-channel method for multiplexing optical signals of multiple sub-channels using OFDM, Nyquist-WDM, or the like and transmitting the multiple optical signals as a single optical signal.
Examples of related art are Japanese Laid-open Patent Publications Nos. 2012-175417 and 2013-201495.